Zettai Kekkonsuru Man vs Zettai Kekkonshinai Woman

"Please marry me." "No, I can't." When Kosuke, the vice president of a client company, suddenly proposes marriage to Tetsuko, she reflexively refuses, having no interest in marriage at all. But that was only the start of Kosuke's fierce attack! "Please fall in love with me." Tetsuko's body shivered at the sound of Kosuke's passionate voice. Every time she sees him, she is surprised by his displays of affection. When he pulls her into his arms and kisses her, it feels so good that she gets weak. At this rate… The marriage battle between an elite heir and a stubborn girl. (Source: Opal Bunko, translated)